First report on Rhabdocoela (Rhabditophora) from deep parts of Skagerrak, with the description of four new species

Abstract

In this contribution we report on 13 species of Rhabdocoela, found during a marine inventory of Skagerrak by the Swedish Taxonomy Initiative. Four new species are described, two of which are Kalyptorhynchia (Gnathorhychidae and Polycystididae) and two belong to Dalytyphloplanoida (Solenopharyngidae). Uncinorhynchus vorago sp. nov., (Gnathorhynchidae) has a triangular stylet consisting of a double-folded plate, which proximally forms a tube, but without a distal, needle-shaped tip. Austrorhynchus artoisi sp. nov. (Polycystididae), has two prostate stylets. Prostate stylet type II consists of a distal tube and a short proximal funnel, which has a stirrup-shaped ornament, whereas the stylet type III shows an unpronounced foot and style connected to each other by a narrow clasp and a comb-bearing plate. The foot and plate are connected to a thread-like flagellum. Lenopharynx bathos sp. nov. (Solenopharyngidae) resembles Lenopharynx tubatus Schockaert & Martens, 1985, but differs in the detailed structure of the stylet and by the lack of colouration and eyes. Proceropharynx profundum sp. nov. has a unique combination of small spines and hard ridges on the cirrus. Additional data are given for the remaining nine species, three of which are new for the Swedish fauna. Espegrendia norvegica Westblad, 1954 (Solenopharyngidae) is redescribed. For the sake of completeness, two more species are mentioned. One is identified as a new species of Acrumena Brunet, but lack of material prevents its formal description. The second one is probably a representative of the taxon Ceratopera Den Hartog, but cannot be identified with certainty because of the poor quality of the preserved material. This contribution is one of very few reports on Rhabdocoela collected from a depth exceeding 100 m and some preliminary biogeographical remarks are therefore given.